1. Field of the Invention
The invention relates to an integrated broadband antenna device, and more particularly to a broadband antenna device which integrates various kinds of antennas to obtain a wider bandwidth.
2. Description of the Prior Art
The personal mobile communication technology has shown its immense potential and commercial value in the wireless communication industry. During its developing process, various systems adopting different techniques and channels have appeared, and they are applied to different geographic areas and markets. However, these differences bring much inconvenience to the manufacturers and customers, and the worst of all, these systems also use different frequencies such as GSM850, DCS1800 and UMTS.
Engineers in this field are trying their best to design a broadband integrated products in order to provide more convenience to users. However, the antenna is the key part when designing the mobile communication products, it is the starting point as well as the ending point of the wireless communication and its characteristics directly influence the transmission quality of the wireless signals. Therefore, the antenna device should meet the following requirements:
1. Frequency and Bandwidth
2. Radiating efficiency and radiating pattern of the antenna
Since the design trend of electronic products towards lightness, thinness, shortness and smallness, the sizes of the antennas for communication products are becoming smaller and smaller. A Planar Inverted-F Antenna (referred to “PIFA”hereinafter) that operates as a ¼ wavelength and can greatly decrease the size is extensively used as an inner-hidden antenna. A conventional PIFA shown in U.S. Pat. No. 5,764,190 can operate at a single frequency. In order to operate at multiple frequencies, PIFA defines an L-shaped slot or U-shaped groove on its radiation metal sheet to obtain multiple operational frequencies.
FIG. 1 shows another conventional antenna having multiple operational frequencies. The antenna device comprises a first radiation portion A, a second radiation portion B and a ground portion C. The first radiation portion A and the second radiation portion B extend respectively from both opposite sides of the same end of the ground portion C. The first radiation portion A comprises a first conductive patch A1 parallel to the ground portion C and a first connection portion A2 connected with the first conductive patch A1 and the ground portion C. The second radiation portion B comprises a second conductive patch B1 parallel to the ground portion C and a second connection portion B2 connected with the second conductive patch B1 and the ground portion C. The first conductive patch A1 and the second conductive patch B1 extend in the same direction from the first connection portion A2 and the second connection portion B2 respectively.
However, even the above-mentioned antennas can operate at multiple frequencies, they have the some disadvantages stated below. The first conductive patch A1 and the second conductive patch B1 are closely disposed, so the bandwidths for both low frequency and high frequency are not enough to cover various system frequency bands. Further, both feeding wire and the feeding point are close to the first connection portion A2, and such an arrangement is a conventional inverted-F antenna device which has a limited bandwidth and can not achieve a wider bandwidth.
The invention solves the above-mentioned problems by providing an integrated broadband antenna device. The antenna device integrates both characteristics and structures of various antennas including a monopole antenna, an inverted-F antenna and a parasitic antenna to produce a wide band and broadband functions simultaneously. Therefore, the antenna device according to the present invention not only has an innovative structure, but also greatly enlarges the frequency range to cover various system frequency bands. Obviously, the high application value is self-evident.